Anolyte liquid level control for chlor-alkali diaphragm cells



A. T. EMERY ET AL Feb. 4, 1969 ANOLYTE LIQUID LEVEL CONTROL FORCHLOR-ALKALI DIAPHRAGM CELLS Filed Nov. 29, 1965 United States Patent O3,425,928 ANOLYTE LIQUID LEVEL CONTROL FOR CHLOR-ALKALI DIAPHRAGM CELLSAlvin T. Emery, North Tonawanda, and Charles W. Schmidtke, NiagaraFalls, N.Y., assignors to Hooker Chemical Corporation, Niagara Falls,N.Y., a corporation of New York Filed Nov. 29, 1965, Ser. No. 510,179U.S. Cl. 204-263 Int. Cl. B01k 3/00 5 Claims ABSTRACT OF THE DISCLOSUREThis invention relates to an anolyte liquid level control device forChlor-alkali cells and more particularly to an apparatus for thewithdrawal of anolyte solution from a chlor-alkali diaphragm cell whilemaintaining a predetermined liquid level within the anolyte compartment.

It has recently been found to be desirable to operate a Chlor-alkalidiaphragm cell utilizing an anolyte recirculation method wherein brinefeed .solution is fed to the anolyte -compartment of a Chlor-alkali cellat a rate greater than that at which the feed solution flows through thediaphragm into the catholyte compartment. In the operation of theanolyte recirculation method, it is yalso desirable to maintain acertain liquid level within the Ianolyte compartment which levelprovides a hydrostatic head which brings pressure to bear upon thediaphragm thereby forcing liquid through the diaphragm. It is furtherdesirable to be able to change the hydrostatic head within the anolytecompartment to provide for changes in operating procedures, therebyregulating the ow rate of anolyte liquor through the diap'hragm into thecatholyte compartment.

It is an object of the present invention to provide an apparatus for thewithdrawal of excess brine feed solution from an anolyte compantment ofa Chlor-alkali cell diaphragm cell. Another object of the presentinvention is to provide `an apparatus for the control of the liquidlevel within an anolyte compartment of such cells. These and otherobject-s will become apparent to those skilled in the art from thedescription of the invention which follows.

In accordance with the invention there is provided an anolyte liquorwithdrawal means for a Chlor-alkali diaphragm cell comprising apassageway for liquids such as a tube, said passageway having an inletmeans and an outlet means for liquids, said inlet means being positionedwithin the anolyte compartment of said cell and said outlet means beingpositioned external to the anolyte compartment of said cell, therebyproviding for the removal of anolyte liquor from said anolytecompartment. In a preferred embodiment of the present invention, thedescribed passageway is a curved tube or pipe capable of being moved, asby rotation, so as to raise and lower the inlet means within the anolytecompartment thereby regulating the anolyte liquid level.

The invention will be more readily described by reference to thedrawings in which;

FIG. 1 is a partial sectional view ot' a chlor-alkali diaphragm cellshowing the apparatus of the present invention located on the sidewallof the cell; and

3,425,928 Patented Feb. 4, 1969 ICC FIG. 2 is a side elevational view ofsaid apparatus.

The apparatus of the present invention is preferably mounted on a celltop 10 of a chlor-alkali cell :in a position such that passageway tube12 extends into the anolyte compartment 14 of said chlor-alkali cell.Tube 12 has liquid inlet means 16 and outlet means 18, the inlet means16 regulating the anolyte liquid level 20 within the anolyte compartment14 by withdrawal of liquid through tube 12 and 4the discharging of itfrom the cell through outlet means 18. The chlor-alkali cell has brinefeed means 22 and chlorine withdrawal means 24 in communication withanolyte compartment 14. In the operation of the cell, brine is fedthrough brine feed means 22 into anolyte compartment 14 from whence itpasses into the catholyte compartment 26 by passing through diaphragm28. Cell liquor, brine containing sodium hydroxide, is withdrawn fromthe catholyte compartment by means of overflow pipe 25. In the operationof the anolyte recirculation method, the brine feed rate is greater thanthe rate at which the brine passes from the anolyte compartment 14through the diaphragm 28 into the catholyte compartment 26. This excessbrine is Withdrawn from the anolyte compartment 14 by means of tube 12.

Tube 12 preferably has a bend or curvature therein equal to an arc ofabout 10 -to 90 degrees. The curved configuration provides clearance forrotation of the tube about an axis passing through the center of cellwall hole 30 Without causing tube 12 to strike the walls of the anolytecompartment. In this preferred embodiment, tube 12 can be rotated in aplane within the anolyte compartment, degrees and more from thevertical. Thus, the anolyte liquid level 20 can be raised to Withinabout -a halfinch for so of the top of the anolyte compartment of thechloralkali cell and lowered to the level of cell wall hole 30. Such achange in anolyte liquid level 20 changes the hydrostatic pressurewithin the cell and effects the flow of liquid through diaphragm 28.Thus the How of anolyte liquor through the diaphragm 28 can be regulatedby changing anolyte liquid level 20. A higher liquid level 20 increasesthe hydrostatic pressure and, as such, increases the flow rate throughthe diaphragm.

Tube 12 is of a diameter suicient to withdraw anolyte liquor at a rateapproaching that lat which brine is fed to the anolyte compartment.Since the brine is often fed to the anolyte compartment under pressure,and whereas the flow through tube 12 is primarily by means of gravity,the diameter of tube 12 is preferably about equal to or larger thanbrine feed means 22. Normally, tube 12 has an inside cross-sectionalarea equal to about l to 5 times the inside cross-sectional area ofbrine feed means 22. The preferred tube diameter use is preferably largeenough to also vent gases throug'h the tube while withdrawing liquidanolyte.

Tube 12 may be constructed of any material substantially inert to theconditions existing within the cell. Such conditions include operatingtemperatures within the range of about 90 to 110 degrees centigradewhile submerged in a concentrated salt (NaCl) solution saturated withchlorine. In addition, such material of construction is preferablycapable of withstanding chlorine attack at a pH in the range of about lto 7. Also, such materials are preferably electrically nonconductive toavoid loss of electrical current. It has been found, that varioussynther tic polymers such as polyvinylidene chloride, after chlorinatedpolyvinyl chloride, chlorinated polyesters, chlorinated rubbers, and thelike materials can be used. Glass and ceramic and various metals such astantalum, titanium and the like can also be used as the passagewaymaterial.

As an aid to adjusting the liquid level 20 within the cell, there ispreferably provided sight glass 31 which -shows the anolyte level. Also,handle 32 is provided on stem 34 of tube 12 to aid in rotating the tubewhen adjusting liquid level 20.

Outlet means 18 of tube 12, passes withdrawn anolyte liquor towtihdrawal pipe 36. Withdrawal pipe 36 has sight glass 38 through whichobservations of the liquor being withdrawn from the anolyte compartment14 and the ow rate thereof can be made.

As will be readily recognized by those skilled in the art, variousmodifications of the present apparatus can be made without departingfrom the spirit thereof. The particular shape and design of the tube canbe changed to meet the particular shape and design of the tube can bechanged to meet the particular cell requirements and to provide forvarious methods of changing the liquid level other than by rotating thetube. One such method which is readily apparent from the presentdisclosure is to provide means for the partial withdrawal of the tubefrom the anolyte compartment thereby lowering or raising the anolytelevel as desired.

While there have been described various embodiments of the presentinvention, the apparatus described is not intended to be understood aslimiting the scope of the invention, as it is realized that changestherein are possible. It is further intended that each element recitedin any of t'he following claims is to be understood as referring to allequivalent elements for accomplishing substantially the same results insubstantially the same or equivalent manner. It is intended to cover theinvention broadly in whatever form its principles may be utilized.

What is claimed is:

1. In a Chlor-alkali diaphragm cell comprising an anolyte compartmentseparated from a catholyte compartment by a porous diaphragm, saidanolyte compartment comprising an anode, brine feed means and chlorinegas withdrawal means, the improvement which is an anolyte liquorwithdrawal means comprising a passageway for t'he passage of anolytehaving an inlet means capable of being raised and lowered to change theliquid level within the anolyte compartment of said cell and an outletmeans positioned external to the anolyte compartment of said cellthereby providing for the removal of anolyte liquor from said anolytecompartment.

2. The apparatus of claim 1 wherein a sight glass means is positioned onsaid outlet means for the observation of liquid ilow.

3. The apparatus of claim 1 wherein the passageway for liquids is a tubehaving a curvature therein equal to an arc of about 10 to 90 degrees,said curved tube having means for the rotation thereof in said anolytecompartment within a plane having an angle of up to about degrees fromthe vertical, thereby raising and lowering the inlet means of said tubewithin said anolyte compartrnent.

4. The apparatus of claim 1 wherein said passageway for liquids hasgaseous Venting means associated therewith.

5. The apparatus of claim 3 wherein said passageway for liquids is ofsufficient capacity to provide for the venting of gases whilewithdrawing said anolyte liquor.

References Cited UNITED STATES PATENTS 1,884,855 10/1932 Pryce137-247.51 1,930,618 10/1933 Jones et al. 137-579 XR 2,460,159 1/1949White 137-579 XR 2,867,213 1/1959 Thomas 137-559 XR 3,301,310 1/1967Sperber et al. 137-579 XR 1,558,085 10/1925 Giordani et al. 204-266HENRY T. KLINKSIEK, Primary Examiner.

U.S. Cl. X.R.

ggsgg UNTTED STATES PATENT OFFICE CERTIFICATE 0F CGRRECTION DatedFebruary l4, 1969 Patent No. 3,l+25,928

Invent0r(s) Alvin T. Emery and Charles w. Schmidtke It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

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